442 THE JOURNAL OF GEOLOGY. 
Lithology.—VYhe Merced series of the Santa Cruz Moun- 
tains is composed of a great thickness of partly consolidated 
sands, clays, argillaceous sands and hard fine conglomerates. 
The most abundant and characteristic rock is a dark drab or 
slate-colored argillaceous sand, breaking into small fragments of 
about half an inch cube, frequently with bright red or yellow faces. 
It varies in hardness from that which crushes easily in the hand 
to more argillaceous varieties which are tough like clay. A soft 
yellow or buff-colored sand is quite common, and along Seven 
Mile Beach there are many thin layers of hard conglomerate, 
usually containing many fragments of shells. Occasionally 
shells are so abundant as to form shell breccia. 
Near the top of the section on Seven Mile Beach the strata 
become more and more unconsolidated and sandy, the upper 
layers consisting almost entirely of soft yellow and orange-col- 
ored sand. Near the top is a soft, white, chalky layer, from one 
to six feet thick, which Dr. Lawson considers a volcanic ash.% 
Stratigraphy.—The section along Seven Mile Beach has a 
thickness of about 4500 feet; it is not complete, however, but is 
cut off at the bottom and south end by the great fault which 
runs from Mussel Rock to Black Mountain. The lower or 
Transition beds are exposed south of Half Moon Bay, but no 
way of connecting them with the Seven Mile Beach section 
was found. Near San Gregorio about 500 feet of strata is 
exposed. 
LNstribution—The Merced series, antedating as it does the 
upheaval which gives the Santa Cruz Mountains its present topo- 
graphic position, was probably originally laid down over all or 
most of the region now occupied by these mountains. Pleisto- 
cene movements have preserved the lower deposits, while ero- 
sion has removed the strata from the upper parts of the range. 
It seems possible that most of the beds in different parts of 
the state from which older Pliocene fossils have been reported 
will be found to correspond with this series. Dr. Lawson 
believes that the one he recently described as the ‘Wild Cat 
* Univ. of Cal., Bull. Dept. Geol., I., 144. 
